Heteropolyacids and their salts have been effectively used in selective catalytic reduction because of the Keggin structure and extraordinarily strong acidity. Catalysts with and without the Keggin ...structure were synthesized to further investigate the effects of heteropolyoxometallate on low temperature NH.sub.3-SCR. XRD, BET, Raman, H.sub.2-TPR, NH.sub.3-TPD, FT-IR, and SO.sub.2-TPD techniques were used to characterize the physicochemical characteristics of the catalysts. Results indicate that catalysts with the Keggin structure had more surface Brönsted and Lewis acid sites, and these catalysts had significantly improved performances in the SCR reaction and in SO.sub.2 poisoning resistance. Graphical
NiO has been found to be highly outstanding in producing Hsub.2 and Osub.2 from Hsub.2O through magnetic stirring, while its capability for the reduction of COsub.2 through mechanical stimulation has ...not been investigated. Presently, NiO particles have been employed to promote the conversion of Hsub.2O and COsub.2 enclosed in reactors into flammable gases through magnetic stirring. For a 150 mL glass reactor filled with 50 mL water, 1.00 g of NiO particles, and 1 atm of COsub.2, 24 h of magnetic stirring using a home-made Teflon magnetic rotary disk resulted in the formation of 33.80 ppm CO, 10.10 ppm CHsub.4, and 12,868.80 ppm Hsub.2. More importantly, the reduction of COsub.2 was found to be substantially enhanced through coating some polymers and metals on the reactor bottoms, including 25.64 ppm CO and 70.97 ppm CHsub.4 obtained for a PVC-coated reactor and 30.68 ppm CO, 52.78 ppm CHsub.4, 3.82 ppm Csub.2Hsub.6, and 2.18 ppm Csub.2Hsub.4 obtained for a stainless steel-coated reactor. Hydroxyl radicals were detected using fluorescence spectroscopy for NiO particles under magnetic stirring in water. A tribo-catalytic mechanism has been proposed for the conversion of Hsub.2O and COsub.2 into flammable gases by NiO particles under magnetic stirring that is based on the excitation of electron-hole pairs in NiO by mechanical energy absorbed through friction. These findings not only reveal a great potential for mechanical energy to be utilized for COsub.2 conversion but are also valuable for fundamental studies.
In reactions restricted previously to a ruthenium catalyst, a 1-lithium-2-alkyl-1,2-dihydropyridine complex is shown to be a competitive alternative dehydrogenation catalyst for the transformation of ...diamine boranes into cyclic 1,3,2-diazaborolidines, which can in turn be smoothly arylated in good yields. This study established the conditions and solvent dependence of the catalysis through NMR monitoring, with mechanistic insight provided by NMR (including DOSY) experiments and X-ray crystallographic studies of several model lithio intermediates.
The first asymmetric 3+2 cycloaddition of vinyl aziridines with alpha,beta-unsaturated aldehydes, based on synergistic catalysis, is disclosed. This methodology allows the formation of attractive ...pyrrolidine structures in good yields (up to 84%), moderate diastereoselectivity, and high enantioselectivity values (up to >99% ee). Additionally, a tricyclic pyrrolidine core structure found in biologically active molecules was synthesized in a one-pot fashion by using the presented reaction concept. Finally, a mechanistic proposal is outlined.
A divergent strategy is presented for the synthesis of 1,3-di- and 1,3,4-trisubstituted beta-carbolines through an unprecedented one-pot triple-orthogonal-metal relay catalysis, and 1,3-disubstituted ...4-hydroxy-beta-carbolines through a one-pot bimetallic relay catalysis from readily accessible 3-(2-aminophenyl)-5-hexenyn-3-ols. These strategies were elaborated to enable the synthesis of benzofuro2,3-cpyridines, benzothieno2,3-cpyridines, and isoquinolines, which otherwise require multistep synthesis.
Reaction of 5,6‐dihydro‐4H‐pyrrolo3,2,1‐ijquinoline‐1,2‐dione (3) with two equivalents of cyclic 1,3‐dicarbonyl compounds under acid catalysis generates spiro4H‐pyran‐3,3′‐oxindoles 7. In contrast, ...though base catalysis also achieves double addition, the final products 8 result from subsequent ring opening of the five‐membered lactam via intramolecular attack by enolate; these products can be converted into the spiro4H‐pyran‐3,3′‐oxindoles by treatment with acid.
The acid-catalyzed rearrangement of epoxides 3a, 4a, 6a, and 7a derived from beta-himachalene, the major constituent of Cedrus atlantica essential oil, has been studied using various Lewis and ...Bronsted acids. Several new enantiomerically pure ketones were obtained in good yields and high selectivities. All products obtained were fully characterized by .sup.1H and .sup.13C NMR, and the mechanistic explanations for their formation were proposed.
Armido Studer
European journal of organic chemistry,
July 13, 2018, Volume:
2018, Issue:
26
Journal Article
Peer reviewed
“We are currently trying to push the boundaries of ‘electron‐catalysis’.” Find out more about this author's research at https://doi.org/10.1002/ejoc.201800583.
“We are currently trying to push the ...boundaries of ‘electron‐catalysis’.” Find out more about this author's research at https://doi.org/10.1002/ejoc.201800583.
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